Exploring the impact of aquaculture sludge on the swell-shrink behavior of expansive clays

Abstract

Aquaculture is practiced in many countries including India; coastal region of Andhra Pradesh is known for its intensive aquaculture farming. Sludge obtained from these farms was used to fill low-lying areas during summer. Aquaculture sludge (AS) is an organic material generated at the bottom of the aquaculture pond produced from shrimp effluents, chemical usage, unsustainable feed, minerals, and disinfectants. It is a polluting material that requires care and attention. This work aims to evaluate the effect of the mixing of aquaculture sludge on the geotechnical properties of clay subsoil. Plasticity, compaction characteristics, and one-dimensional swell consolidation tests were performed on expansive blended clays. The results of the swell-shrink behavior of expansive clays mixed with AS show a significant decrease in swelling phenomenon. Microstructural analysis of expansive clay and clay mixed with AS was carried out using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction (XRD) tests to understand the surface textures, particle sizes, and chemical reactions. Microstructural analysis revealed the development of a crystalline structure with a C-S-H gel and CaCO3. In addition, it also shows the development of flocs and the aggregation of clay particles with AS.

Keywords

• Aquaculture sludge
• Expansive clays
• Micro-structure
• Swelling
• Shrinkage